准噶尔盆地东部石炭系凝灰质烃源岩有机质富集机制

The organic-rich tuffaceous mudstones and tuffs had been widely developed in the eastern Junggar basin during the latter of Early Carboniferous - the end of Late Carboniferous. These tuffaceous rocks are considered an important source rocks for the volcanic reservoirs in Carboniferous, however, it is hard to evaluate the potential source and distribution pattern due to the lack of study on enrichment mechanism for organic matter in these tuffaceous source. The project plans to observe the overlying relationship between organic matters and inorganic minerals by microscope and scanning electron microscopy (SEM) analysis, and examine the dependency of organic matter and inorganic mineral through the determination of the total organic carbon, the content of clay mineral, major elements. The trace elements, rare earth elements, biomarker and monomer isotope will be measured to analyze the contribution of organic matter source and depositional environment, and select a group of organic and inorganic geochemistry data with well correlation. The project will establish the mode of trace organic – inorganic interaction during organic matter production, organic matter occurrence and preservation, and identify the intrinsic links of volcanic eruption, hydrothermal activity, terrestrial input, lake primary productivity and redox conditions, and which effects impact on the process of organic enrichment. Combine the above research on tuffaceous mudstones and tuffs, the project will established the enrichment mechanism of organic matters in tuffaceous sources rocks, which could provide a scientific basis for oil and gas exploration in the study area.

准噶尔盆地东部石炭系广泛发育富含有机质的凝灰质泥岩和沉凝灰岩，这些凝灰质烃源岩为石炭系火山岩油气藏提供可靠油气源保障，但是由于国内外对凝灰质烃源岩有机质富集机制研究较少，对其进行资源评价和分布预测缺乏一定的科学依据。本项目通过对烃源岩显微观察和岩矿鉴定，分析有机质与无机矿物叠置关系。测定有机碳、主量元素、粘土矿物含量，确定有机质与无机矿物依附关系。通过对烃源岩微量元素、稀土元素、生物标志化合物和单体同位素测定，分析有机质的贡献源和沉积环境，遴选出联系相对密切的有机与无机地球化学数据，结合有机质与矿物空间叠置和依附关系，追踪有机质生产、赋存和保存过程中有机－无机相互作用的事件主体和作用方式，查明火山喷发、热液活动、陆源输入、湖水初级生产力和水体氧化还化条件等因素的内在联系，以及各因素在有机质富集各环节影响方式，建立凝灰质烃源岩有机质富集机制，为研究区及类似地区油气勘探提供科学依据。

准噶尔盆地东部石炭系凝灰质源岩发育于火山活动间歇期，其分布广泛且有机质丰度均高于有效烃源岩下限标准，凝灰质烃源岩可以作为石炭系火山岩油气藏可靠源岩。开展凝灰质烃源岩有机质富集机制研究，不但有助于了解火山活动背景下有机质生成和保存，为研究区资源评价与分布预测提供科学依据，而且对于指导新疆北部石炭系火山岩油气勘探，进行深部油气资源评价具有重要实践意义。凝灰质烃源岩有机质富集过程实际上是岩石圈与水圈相互作用的结果，项目初衷通过元素地球化学与有机地球化学指标的相互关系寻找有机无机相互作用，通过大量数据统计显示，准东地区凝灰质烃源岩中两者并没有明显相关性，然而烃源岩评价与气源对比均表明，石炭系巴山组凝灰质烃源岩作为准东地区重要的烃源岩为火山岩油气藏提供了可观的气源供给。生物地球化学指标显示有机质来源于陆源蕨类植物，烃源岩沉积环境为陆内裂陷地区具有海相特征的咸水湖环境，因此凝灰质烃源形成过程中的有机无机相互作用可能更多体现在火山灰对土壤营养成份的贡献，而这种能量与物质转移并不能通过凝灰质烃源岩本身特征直接反映出来。通过有机质-粘土矿物-金属离子吸附模拟发现：酸性条件下适量的金属离子明显促进了伊利石对腐殖酸（有机质主要组成部分）吸附，同时碱性条件下金属离子也能够促进了伊利石对腐殖酸吸附，说明粘土矿物对有机质吸附是一个复杂的有机-无机相互作用过程，同时证实了也巴山组时期碱性水体环境中火山物质中金属离子有助于粘土矿物对有机质吸附。